feat(chat): per-user inbox anchor for listing kind=value threads

EA2 doesn't expose a generic flow-by-kind list endpoint; flow/processes
is definition-only. Migrated chat to flow.kind=value, so direct listing
needed a new strategy.

- Each user has a deterministic inbox flow.kind=value doc keyed by
  email slug. ensureInbox() creates it idempotently on first listThreads.
- createThread links the new thread into BOTH participants' inboxes via
  defines edges with role='presentation' (each link is one apply-batch).
- listThreads(userEmail) reads defines edges from the user's inbox key.
  No more reliance on source_context regex filtering through the
  definition catalogue.

Updated all 3 call sites: Chat.tsx (mount + after-create refresh) and
agentTools.send_chat. 31/31 tests green.

src/lib/agentTools.ts

@@ -107,7 +107,7 @@ const TOOLS: ToolDef[] = [
       };
       const recipient = Object.entries(directory).find(([k]) => target.includes(k))?.[1];
       if (!recipient) return { ok: false, display: `I don't know who "${target}" is. Try Mariana, Aisha, or Rohan.` };
-      const threads = await chatApi.listThreads();
+      const threads = await chatApi.listThreads(ctx.userEmail);
       const existing = threads.find((t) => t.participants.includes(recipient) && t.participants.includes(ctx.userEmail));
       const threadKey = existing?._key || (await chatApi.createThread(`${ctx.userEmail} ↔ ${recipient}`, [ctx.userEmail, recipient]));
       await chatApi.sendMessage(threadKey, body, ctx.userEmail);

src/lib/chatApi.ts

@@ -31,6 +31,49 @@ function newRequestId(): string {
   return `chat-${Date.now()}-${Math.random().toString(36).slice(2, 12)}`;
 }
 
+function inboxKeyFor(email: string): string {
+  const slug = email.toLowerCase().replace(/[^a-z0-9]+/g, "_").slice(0, 60);
+  return `inbox_${slug}`;
+}
+
+async function ensureInbox(inboxKey: string, email: string, signal?: AbortSignal): Promise<boolean> {
+  try {
+    const head = await fetch(`${api.config.baseUrl}/api/ea2/flow/${inboxKey}`, { headers: authHeaders(), signal });
+    if (head.ok) return true;
+  } catch { /* fall through */ }
+  const created = await fetch(`${api.config.baseUrl}/api/ea2/flow`, {
+    method: "POST",
+    headers: authHeaders(),
+    body: JSON.stringify({
+      _key: inboxKey,
+      kind: "value",
+      status: "published",
+      name: inboxKey,
+      display_name: `Inbox · ${email}`,
+      description: `Chat inbox anchor for ${email}`,
+      source_context: "CANVAS_CHAT_INBOX",
+      config: { chat: { owner_email: email } },
+    }),
+    signal,
+  });
+  return created.ok || created.status === 409;
+}
+
+async function linkThreadToInbox(inboxKey: string, threadKey: string, signal?: AbortSignal): Promise<void> {
+  const body = {
+    request_id: newRequestId(),
+    ops: [
+      { op: "create_edge", edge_coll: "defines", from: `flow/${inboxKey}`, to: `flow/${threadKey}`, role: "presentation" },
+    ],
+  };
+  await fetch(`${api.config.baseUrl}/api/ea2/apply-batch`, {
+    method: "POST",
+    headers: authHeaders(),
+    body: JSON.stringify(body),
+    signal,
+  });
+}
+
 function authHeaders(): Record<string, string> {
   return {
     Authorization: `Bearer ${sessionStorage.getItem("fm.mc.token.v1")}`,
@@ -48,19 +91,36 @@ async function jsonFetch(path: string, init?: RequestInit) {
 }
 
 export const chatApi = {
-  /** List existing chat-thread flow docs (kind=value, source_context=CANVAS_CHAT_THREAD). */
-  async listThreads(signal?: AbortSignal): Promise<ChatThread[]> {
-    const res = await jsonFetch(`/api/ea2/flow/processes?limit=500&kind=value`, { signal });
-    const items = (res?.items || []) as any[];
-    return items
-      .filter((it) => it?.source_context === "CANVAS_CHAT_THREAD")
-      .map((it) => ({
-        _key: it._key,
-        display_name: it.display_name || "Chat",
-        description: it.description || "",
-        created_at: it.created_at,
-        participants: it.config?.chat?.participants || [],
-      }));
+  /**
+   * List chat threads via the per-user inbox anchor and defines edges. Per-tenant
+   * tenant_id of the inbox is implicit from the Bearer token.
+   */
+  async listThreads(userEmail: string, signal?: AbortSignal): Promise<ChatThread[]> {
+    const inboxKey = inboxKeyFor(userEmail);
+    const inbox = await ensureInbox(inboxKey, userEmail, signal);
+    if (!inbox) return [];
+    const edges = await jsonFetch(`/api/ea2/edges/defines?from=flow/${inboxKey}&limit=200`, { signal });
+    const threadKeys = ((edges?.items || []) as any[])
+      .filter((e) => e?.role === "presentation")
+      .map((e) => (e._to || "").split("/").pop())
+      .filter(Boolean) as string[];
+    const threads = await Promise.all(
+      threadKeys.map(async (k) => {
+        try {
+          const doc = await jsonFetch(`/api/ea2/flow/${k}`, { signal });
+          return {
+            _key: doc._key,
+            display_name: doc.display_name || "Chat",
+            description: doc.description || "",
+            created_at: doc.created_at,
+            participants: doc.config?.chat?.participants || [],
+          } as ChatThread;
+        } catch {
+          return null;
+        }
+      })
+    );
+    return threads.filter((t): t is ChatThread => !!t).sort((a, b) => (b.created_at || "").localeCompare(a.created_at || ""));
   },
 
   /**
@@ -85,7 +145,15 @@ export const chatApi = {
     });
     if (!res.ok) throw new Error(`createThread ${res.status}`);
     const body = await res.json();
-    return body._key;
+    const threadKey = body._key as string;
+    await Promise.all(
+      participants.map(async (email) => {
+        const inboxKey = inboxKeyFor(email);
+        await ensureInbox(inboxKey, email, signal);
+        await linkThreadToInbox(inboxKey, threadKey, signal);
+      })
+    );
+    return threadKey;
   },
 
   /** Read every message under a thread via the edges endpoint. */

src/scenes/Chat.tsx

@@ -34,7 +34,7 @@ export default function Chat() {
     let cancelled = false;
     setLoadingThreads(true);
     chatApi
-      .listThreads()
+      .listThreads(me)
       .then((rows) => {
         if (cancelled) return;
         setThreads(rows);
@@ -73,7 +73,7 @@ export default function Chat() {
     try {
       const otherLabel = personaLabel(recipient);
       const key = await chatApi.createThread(`${personaLabel(me)} ↔ ${otherLabel}`, [me, recipient]);
-      const next = await chatApi.listThreads();
+      const next = await chatApi.listThreads(me);
       setThreads(next);
       setActiveKey(key);
       pushToast("ok", `Thread opened with ${otherLabel}`);